I never understood why electrons have spin... until now!

Electrons don't really spin. Yet, every chemistry teacher will tell you they do. Everyday. Why do they do that? What does the 'spin' really mean?
In this video, we will explore the idea of spin angular momentum. We will see how electrons precess in the presence of an external magnetic field, just like how a spinning table top does.
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[@Picasso_Picante92]

59. I am 59 years old. Studied physics in high school and university. Read many many popular science books written by all the greats. And in 15 minutes you helped me understand something that never ever made sense to me. Thank you dear friend. You have a new subscriber.

[@dp5475]

40+ (let's say) year old engineer. Same hear.

[@edwardofgreene]

58 here. Ditto.

[@BogdanBaudis]

Same here, down to the point, simple enough but not simplistic, Bravo!

[@bhisham2687]

Study with focus and have imagination😅

[@bijukumarkn4626]

yes, i feel the same, Thank you.

[@Summerisle1961]

I love your conversations with Einstein/Feynman etc. They really bring the concepts to life.

[@Batwam0]

I know right, I was thinking gosh, he is so lucky having been able to talk to all these famous scientists!

[@jesublade356]

They are dead tho ☠☠

[@forkenstein]

@@jesublade356 no shit sherlock

[@termitetoxin7983]

@@jesublade356yeah with that attitude

[@giancarloarcenal622]

wth! when? @@jesublade356

[@egotist-ical]

I love this guy, I genuinely NEED to see a gold play button somewhere in the background somewhere in the near future.

[@meepmeep1329]

Yes for the gold play button, but no for the showy part 😅 KZbin doesn't need to be talking about KZbin.

[@debosmitadey2688]

He should the diamond one real quick

[@jamesh318]

This is a very good explanation. As an old physicist I can say, I wish we had these powers of visualization decades ago. It took me years to establish a mental model for electron spin, and you’ve done it in a few minutes! To be fair, there was a lot more mathematics involved but an intuitive model is super useful. Perhaps you can explore this further by talking about some of the experiments that established the existence of the electron and its spin and magnetic nature.

[@abdulkhadarainur4348]

Really thank you sir, for keeping this marvelous field of science alive through your memories. Because of our predecessors, we've got a headstart. But don't worry sir, we will further enhance Physics with each coming generation.

[@TailoredReaction]

If you want to totally blow your mind, think of gravity as though a sphere is expanding (getting bigger) at an accelerating rate. To an observer in the vicinity, the sphere appears to exert a "force" away from its center. Then imagine another sphere does the opposite, it contracts (gets smaller) at an ever increasing faster rate. To an observer the sphere would appear to be accelerating away. In the first instance if you were out in space you would have no way of telling whether you were being drawn towards the sphere or the sphere itself is expanding. In the second instance you would have no way of knowing if the sphere is shrinking at an accelerating rate, or if the sphere is moving away from you at an accelerating rate due to some mysterious "dark energy". We could be just like the two frogs in a well. We may be approaching the 'end of physics' unless and until we can get out of our well. I think the first step is to understand you are in a well.

[@abdulkhadarainur4348]

@@TailoredReaction Really thank you. Your insights help a lot.

[@EscapeVelocity1]

As an old physicist, would you be so kind to explain to this joker that electrons not only do not circle, have no angular momentum, no spin, and in truth, they do not exist.

[@jamesh318]

@@EscapeVelocity1 It's all just a simulation lol

[@nealharder]

I love how he refers to experiments that "we" have done, referring to us, team humans, and he's so excited to be on that team!!! Go us!!!! We can do incredible things!!!!

[@Minisynapse]

Agree! It's a part of scientific thinking 😁 We're all in this together, no one can or could have figured it all out alone, and we can all reap the fruits of scientific progress.

[@thisrandomdude_]

HELL YEAH!!!!!!!!!!!! WE HUMANS ARE PRETTY DARN COOL NGL

[@johnjeffreys6440]

ever see the moon model. It doesn't spin either so-to-speak. The same side faces the earth at all times. It's really tough to comprehend.

[@chocoolatey]

​@@johnjeffreys6440 Unless I misunderstood you, the moon actually does rotate, it just turns out that it is tidally locked to Earth and rotates on its axis at the same rate it moves around the Earth giving the illusion it doesn't rotate. But if it didn't rotate we would see the other side of the moon which we never do.

[@johnjeffreys6440]

@@chocoolatey I think it’s analogous to a ball in a sling. A person is spinning the sling the ball will appear to be stationary on its axis from the person’s perspective unless maybe you looking down on it from aBirdseye view. I hate auto correct

[@maxteer2800]

Love this. No fluff, no gimmicks, no editing. Just thoughtful conversation and exposition

[@codingbloke]

What a brilliant way to explain this concept. I'm an avid watcher of physics youtube videos and have seen many that "explain" that quantum spin isn't really spin but most just leave it at that even when that is subject of the video. This "conversation with a physicist" style where you ask the obvious questions that I as viewer would have was really refreshing and informative. I have seen much material already on this subject, I rarely learn anything new, I did today! Well done!

[@Mahesh_Shenoy]

Wow, glad to hear that!

[@melody3741]

@@Mahesh_Shenoythe questions you ask too are SO on point. Most communicator/ news youtubers pose ultra obvious and not very deep questions to themselves. You answering the actual literal questions we have, presumably because you yourself thought of them when trying extremely hard to understand the subject, lets us immediately fill in the hole in our mental model instead of having to figure out where it fits. You are genuinely a gift to the world, thank you so much.

[@raezor82]

The Maheshic Method

[@brucehilton1662]

I was a practicing magnetic resonance spectroscopist in my career, and taught courses that focused on spin dynamics. So it's not an unfamitiar subject to me. Even so, Ifound your presentation insightful and pleasing. Good work.

[@Mahesh_Shenoy]

Wow, that's incredibly encouraging, Bruce. Thanks :)

[@ezdlc2693]

Hi Bruce 🙋‍♂️

[@hillaryclinton2415]

MRI is proton spin, not electron. Edit.. nope.. it's precession of a spinning proton.. not the same thing

[@NicolasSchmidMusic]

It’s physically the same. It’s as if you would say that that the speed of a ball was not the same as the speed of a car. Also some NMR technics actually use electron spin because they get more easely polarized and then transfer this electron spin to nuclear spin by shining a microwave source. This is called « hyperpolarization »

[@rinzhler6922]

​​@@hillaryclinton2415If you check his comment, he mentioned 'spin dynamics' and that 'he is familiar with it' . 🙂

[@jamesblossom-y1u]

Thank you! I have studied physics for 45 years by reading books attending lectures, and asking particle physicists that I worked with at Los Alamos. The usual answer was "you wouldn't understand.' Now you have given me a perspective by actually explaining it. As simple as that.

[@terencehawkes3933]

This is the first time I have ever heard such a clear explanation that I, a layman, can understand. Thank You!

[@jamesmckenzie4572]

I clicked on this randomly and I'm glad I did. You've finally explained electron spin in a way that I can understand and even believe. And with a sense of humour too. I've read about this stuff for a long time and yours is the first explanation that has worked for me. I think you are the first to take the time to not just skim over the peculiar details that need to be understood to make any sense of what spin is. Thank you, and I'm subscribing (and sharing) by virtue of this, the first of your videos that I have seen.

[@Mahesh_Shenoy]

That made my day. That's the exact response I was looking for while planning this video!

[@hakiza-technologyltd.8198]

You’re wrong www.dropbox.com/s/c69trrjillfr23r/HAKIZA-1%20%28draft%29%20-1.pdf?dl=0

[@monoamiga]

SAME HERE! I *FINALLY* understood it! Thanks man!

[@lastchance8142]

The thing about quantum mechanics is that we can't explain it from "first principles". Most of the properties and behaviors we observe are so counterintuitive that they are tantamount to magic! After 100 years, we can describe it well enough to predict results (probablistically), but can't explain "why". Two possibilities present themselves. Either we have reached the ground floor of knowledge and will never understand "why" these behaviors exist, or we have yet to discover something even more fundamental than QM, from which it emerges. Based on the history of all science, I expect the latter.

[@MrSpock-sm3dd]

his explanation is useless and very slow but im glad at least some people liked it

[@thurlravenscroft2572]

I have no idea what you’re talking about. But seeing the joy that sharing this topic brings you, blesses my heart.

[@davidbordwell8346]

Lol

[@grnarsch5287]

Its hard there is a meme. Spin is like a ball that spins. But there is no ball and it doesnt spin. The good thing is that most dont have to understand it. But the calculations still work

[@clintanderson4591]

Legit. Tons of other vids and classes here, yet you still taught me something new--without math and based on intuition. Grow your channel, dude. Standing behind you.

[@draelyc]

I love the way you laid the whole matter out in the form of a "conversation with the master." Very helpful for folks like me, who love to follow the subject but who've got no formal training ... and CERTAINLY don't have the mathematical ability!!! ... to engage the material directly. Thank you!

[@TheSoundSociety_90s]

I have been looking at KZbin videos that explain electron spin for many years. I have been reading about electron spin for many years. I have never understood nor grasped the concept. It has eluded me like nothing else! Your video explaining electron spin is the most clear and concise explanation I have ever seen in my entire journey. It's as though a light bulb has gone off in my head. I now understand! Thank you!

[@danilo49252]

This is an extremely well put and organized way to explain electron spin. I greatly appreciate the humor and the way of narrating through the whole story, and most importantly not omitting the smallest of details that fill in all the little gaps and ultimately form the full picture. Thank you so much for this video!

[@craigwall9536]

If you think he "explained" spin, you will have to UNlearn things later. This guy suffers from a overdose of mysticism. "They can NEVER spin!" Yet they cannot be distinduished from a spinning object? He needs to go back and thin about "observables". And that imcluded the tools in your imagination by which we construct these flawed "Gedanken Experiments". He says it can't spin because nothing extends from a point that can observed circling the axis. So your assertion that a point "CANNOT SPIN" reduces to : connot be OBSERVED to spin" which is NOT the same thing!!!!

[@MrFeanor82]

You’re such an honest teacher, it truly blows me away. There is no ego whatsoever in the way you explain things to the layman. I hope you realize how good of a teacher you are!!

[@rays14ful]

Man you should get some Nobel prize for being able to make complex subjects so simple. Thank you. That was a tremendous explanation.

[@silversurfer493]

He does great videos, i agree. But in this case, especially the "wobble" explanation for the electron in a magnetic field is just not appropriate. It would have been so much easier to show the analogue movement of a "gyroscope" where he can exactly show what is going on (OK, not on the nuclear or electron level but for visualization). This would have also made it much easier to explain (which he misses totally) of how to actually measure the effect. So i consider this one of the weaker videos on this topic.

[@mattp422]

What a beautiful explanation! As an academic radiologist, I have always found it difficult to explain why protons precess in the magnetic field of an MRI. That is, how to reconcile the Newtonian concept of angular momentum with the quantum mechanical theory? Thank you, thank you!

[@shivukumar2564]

KZbin algorithm has finally understood me.

[@KoushikMaji398]

True

[@ObitoUchiha_YT]

frfr

[@nightingale_07_]

So true ​@@ObitoUchiha_YT

[@someone.9813]

Me too.

[@arthurmassenataube8085]

Finally 🙌

[@MonkeysEmperor]

Months of reading about quantum spin and you have brought for this with such clarity! Congrats, amazing

[@SaharaSmith-h2n]

Great video! Ever since high school, any time electron spin was brought up in class, it was always accompanied by the phrase, "the electrons aren't really spinning, but...". So, I asked nearly every chemistry professor that I've ever had what exactly electron spin is, and never got any answers. This has finally put those nagging questions to rest. Thanks!

[@Mahesh_Shenoy]

That was the whole intent, I am glad it helped!

[@tiborbogi7457]

@@Mahesh_Shenoy It would be nice, if there is a link to experiment, that proves electron wobble in magnetic field. Or at least write down name of experiment in description, please.

[@gibbogle]

I get the impression that many physics and chemistry professors don't actually know what electron spin is.

[@AmandaHugandKiss411]

​@@tiborbogi7457I agree, I would like to read about these experiments as well.

[@ianoliver3130]

​@@Mahesh_Shenoythe election doesn't have charge?- it is the charge. If the electron can't rotate,then the charge can't rotate either. So why does it have a magnetic field?

[@mohosinmahmud4238]

Thank you so much. I've been struggling to comprehend this for years. Your ability to explain complex topics in so simple manner is truly remarkable.

[@hamuArt]

I’m not a physicist, but my father studied metallurgical engineering in the early 1970s, and he owned the complete works of Feynman translated into Hungarian. As a teenager in high school, I enjoyed reading them because they explained concepts in an accessible way-something even many university professors struggled to do at the time (maybe nowadays too). On a related note, I remember Edward Teller giving a lecture at ELTE University in the 1990s. What was astonishing was how this generation (Teller, Feynman) were not only excellent speakers but also exceptionally skilled at making highly complex physics understandable to laypeople.

[@kevinfletcher1999]

Thanks mate, you just made my head spin ! 😂😂

[@I_Am_AI_007]

“Individual pieces of cell aren't alive” Mitochondria: 💀

[@AnnuPriya-jm2fr]

He meant consciousness dude

[@ksarz178]

​@@AnnuPriya-jm2frsince when does a cell have consciousness?

[@macfrankist]

He and Feynman are fundamentally wrong.

[@Pseudify]

Life might be even more difficult a concept to define than quantum spin.

[@I_Am_AI_007]

​@@Pseudifytill they realise...

[@sjallard]

Guy, your videos are like the residual FAQ of every other physics video I've watched which didn't bother to explain either well enough or even at all this kind of fundamental topics. I'm binging against my will and available time, but no regrets. Thanks!

[@laurie886]

Fantastic video . I'm a 66 year old man with no physics qualifications at all but I've been reading quantum physics for the past 5 years just as a (unwinding) after work sort of thing I'm hooked on it I just can't get enough and I think your videos are just great thank you ( by the way I find the Richard Feynman lectures volume 1 2 and 3 a great read )

[@Mahesh_Shenoy]

That’s so incredible, Laurie. Super encouraging!

[@laurie886]

Thanks for the reply I look forward to seeing the next video

[@ravikantpatil3398]

Very good

[@shubhamkumar-nw1ui]

Wow.thats inspiring

[@alexandrekassiantchouk1632]

Check Dr. Vivian Robinson video about electron is confined photon/standing electromagnetic wave (Dr. Williamson model of electron) - that explains/gives origin to spin, charge, inertia=mass.

[@AdamAlton]

This seems to me like a strong clue that electrons are in fact *not* fundamental particles and that there is something deeper yet to be discovered. Thanks for the excellent video.

no, even if the electron is not fundamental the momentum would be too high to be explained by anything happening inside of it.

[@DJVil777]

There is also another thing. If electron has a spin axis that going from this tube it would be deflected depending by the angle of the spin axis. In the experiment there is NO dependence. The electrons are eigher deflecting up or down. That is why the electron spin is not a spin. It is some fundumental property of it that cannot be understand by our intuition

[@AmericanDiscord]

@ Lots of theories posit composite electrons. I don't know why you think there is some rule about momentum that would prevent a composite electron. Your statement is self-contradictory, even if it is not composite it's momentum has to be related to whats is happening with the particle.

[@AmericanDiscord]

​@@DJVil777 Electrons can have arbitrarily oriented spin axis, so you are incorrect. That they align themselves in one of two ways in the presence of a magnetic field, has nothing to do with whether "a spin is a spin".

@@AmericanDiscord no, you just don’t understand me. This reason is not mine is the textbook reason, which you would know if you actually studied real physics.

[@tcpip4me]

It took me 30 seconds of your video to subscribe. Perfect down to earth science. Thank you for your work… a great science communicator!!

[@Frank-si2jd]

Incredibly well explained! Thanks for these nice physics tutorials, they are very understandable for “us” non physicists!

[@ignorasmus]

Think of electrons being politicians. They "Behave" as if they care about people, but really, they don't and they can't. 😂

[@Mahesh_Shenoy]

Woah! That sums things up very nicely!

[@eyewaves...]

Good one...prefer science of course...😂

[@0biwan7]

are you saying electrons behave like they can spin but cannot actually spin because they are not made of constituents? are you saying that politicians spin things as if they care about their constituents even they though cannot actually care about their constituents?

[@snehamishra7427]

​@@0biwan7 I guess yes😂

[@atrus3823]

Watched a few of your videos lately. You are really talented at explaining things: clear, methodical, enthusiastic in a genuine way, and most importantly, you lead logically from point to point guided by natural questions that would arise.

[@michaelwobrien]

Great video. You are a talented teacher. Your entertaining and engaging method of explaining complex topics is fantastic.

[@bharathcarrom2159]

I had tried a lot to understand what the Spin really was before this, but had a hard time. This video has taken me the closest towards understanding it. Thank you. Now I think I can move from this reference point.

[@Randori-Music]

I have a hard time understanding anything relating to quantum physics just as a person curious about the topic a bit, but this video is fantastic and made me understand it a bit better. Thank you

[@DurgeshSharma-oz2xb]

Nicely done. I am a hobby physics student at age 47. When I first started QM few years back electron spin bothered me but I was able to overcome that by reading a lot from various sources including Feynman lectures. You have explained this nicely in a short video. I believe there is more to fundamental particles. I have intuition that even electron and other particles have structure and study of which will reveal more. I m sure your videos will encourage more guys to take interest in quantum mechanics. As more people will take interest in physics more Einstiens and Feynmans world will produce. So please keep up the good work and keep these videos rolling out.

[@fhamilton1]

Been self learning QM for some time and this is by far the best explanation of spin. Thanks.

[@citizen127at]

Wow, what a brilliant presentation. I've always just accepted that electrons have spin without really understanding how we arrived at that conclusion, not anymore. Awesome!

[@zepplondon]

After watching several of your videos I grew to need them as much as your microphone needs a pop filter

[@CACBCCCU]

You should try to explain how a non-spinning electron can (or cannot) generate light that carries spinning field vectors (is circularly polarized). All light can be constructed with circularly polarized photons, so it's a critical concept.

[@vXenaiv]

That's because they actually spin😂

[@troybarron9213]

​@@vXenaiv Yes, and if Dr. David L. Bergman's model is correct the electron is indeed a fundamental particle and made of a spinning (or circulating) electric charge with actual physical dimensions. The shape is roughly a toroid (donut), the dimensions give you Plank's constant (not a constant at all, the the answer to an equation involving the two diameters of the toroid). It also gives you the answer to where gravity comes from, better predictor of radio active decay than the standard model (no need to make-up the Strong & Weak nuclear forces. So just one force (Electro-Magnetism & E=m*c^2). If you smash it hard enough you get fleeting energy that can't stabilize and you pretend you understand that by measuring it is bunch of times and calling it quarks.

[@bradwiley1882]

Badass. Nice work. I’ve studied chemistry and quantum mechanics for 45 years and appreciate your approach!

[@mikegale9757]

Excellent presentation. As you say, the issue with electron spin is that the electron has no breadth or if it does, it looks the same from all angles so there's no sense in which it can spin. Black holes have the same problem, but they can have angular momentum, too. The upshot is, angular momentum is more fundamental than we have been led to believe. It is possible to have angular momentum even if you have no breadth or you are devoid of features. It will manifest when you interact with your environment. Photons are another case in point. Planck's constant is effectively a chunk of angular momentum.

[@aaattteeennn]

Such is the wonder of endlessly empty curving space!

[@mattiaandrao1636]

Why from the evideces they didn't derivate that electrons are made of a bunch shorter particles like protons with quarks?

[@varsha_1703]

Mahesh we need QUANTUM MECHANICS from you ...more topics on QM please ❤🙏🛐

[@Mahesh_Shenoy]

Working on it.

[@herbrabe6865]

I consider you as one of the best and honest teachers of physics.

[@praveenb9048]

I just found your channel and I am now bingeing on your excellent videos. I am sure many of us viewers would love to know more about your story -- how did you get started in science education, how did you join Khan academy, what inspired you when you were a kid?

[@Mahesh_Shenoy]

Will do it when I hit a milestone. Say 50k or something?

[@adamlatour4011]

Great explanation, but I have to correct something: the individual particles in your basketball *are* spinning about their own centers as they move in a circular path around the center of the basketball. Here’s another way to think on it: someone standing on the equator will do a full flip head over heels over 24 hours. Someone standing on one of the polls will spin around once over 24 hours. Every point in a solid (rigid) spinning object has an angular velocity equal to the angular velocity of the object it belongs to. Put a coin on a spinning record, or a book on a spinning chair and watch it - it doesn’t “hold still” as it moves in a circular path, it spins too! At exactly the same angular velocity. While it’s hard to conceptually think of a true singular point (i.e., no consituent parts) spinning, explaining this by saying spin is an emergent property of a collection of non-spinning objects moving around a common axis is a bit wrong. A spinning object full of non-spinning consituents would experience a ton of tidal friction. But, the explanation of how we detect the spin of an electron by measuring it’s wobble in a magnetic field is great, so the lesson of the video is still mostly unchanged and really great.

[@clawsoon]

Came here to say this, glad someone said it better than I would've. When something is locked into position in a larger object (like the molecules in a basketball), they will experience one rotation for every revolution. More generally, anything that has an orientable feature can be spun.

[@olmo-c9e]

i do like the way you approach these videos saying you didn't understand how something works, putting you in our boat, and continuing to do so as to not intimidate.

[@BrianSwatton]

This was nicely done. I still don't feel I really understand electron "spin", but now I know precisely what I don't understand 😂. (40 years in electronics too!)

[@nd.c.1098]

Hey sir, you have a talented presentation/ tutoring skills, I work in field of medical physics, your explanations for terms are refreshing ! That makes me recalled the teaching of my old fashioned physics teacher, Thank you :)

[@vaishalitrivedipathak9120]

I just love the excitement that you feel while explaining the theory...

[@GuntherX57]

I'm a chemistry student, and this is a topic I struggle a LOT to understand (my teachers just say "it makes sense when you apply general relativity"). So it's refreshing to see videos like this. Good job!

[@MrMelvinSchlock]

That means they don’t fully understand it. If someone can’t explain something so that a third grader can visualize it they don’t have a good enough handle it. And if it’s not spinning don’t call it spin. By doing so 99.8% of the world has been thrown into confusion.

[@Wes_Jones]

Back in the 70's when I got my degree in physics, none of my professors could explain spin as clearly as you just did.

[@rafaelalexie2417]

By far the most valuable explanation of the quantum world. I would ask exactly the same questions , and the answers are exactly what I needed. Feynman would be proud!

[@rararnanan7244]

A very nice presentation of the topic. Well done! From here, when we look at how much angular momentuum the electron has it gets even wilder. Electrons have spin 1/2 (in Planck constant units). A particle with spin 1 has a symmetry of 1 - that means that if you rotate "it" (meaning its wave function) a full circle it returns to the original state. A particle with spin 2 means that the wave function looks like itself twice in a full turn (think of a rod). A particle with spin 3 repeats itself 3 times in a full turn (e.g., a perfect triangle). This means that in order for the electron with spin 1/2 to return to its original state you have to turn it TWO full circles... this one fried my brain. 😵‍💫

[@ianoliver3130]

Place 2 pound coins together on a piece of paper. As you roll the top coin round the other one without slipping the top coin will complete 2 full rotations as it rotates around the bottom coin once! Try it.

[@BloobleBonker]

We are tantalysingly close to understanding this but still it evades our grasp. Great video. The answer is just around the corner. It's a simple answer, surely.

[@Mahesh_Shenoy]

We do understand it. By using the language of math and quantum mechanics. But we will probably never understand it if we try to use English.

[@danielnigel6920]

@@Mahesh_Shenoyyou are obviously still young and full of yourself

[@aaronmicalowe]

​@@Mahesh_ShenoyI wouldn't trust math alone. Math allows many things to exist in theory that have and never will be observed, because they don't exist in reality. For example, white holes, Klein bottles, time travel, warp fields, negative energy, anti-gravity, etc. Saying quantum spin is not saying anything different than spin unless you define the difference. Quantum spin is still, "trust me bro" logic until it is observed and nothing in your video attempted to say what it is.

[@vXenaiv]

​@@aaronmicaloweexactly my thoughts

[@HyperCubist]

Just saw this video for the second time. This is such an intuitive explanation, thanks!!

[@nohithair]

I really enjoyed listening to you! Thanks so much for sharing a small piece of your mind with me. You communicated an important concept extremely well. I count myself fortunate to have lucked into finding your video here, today. I will definitely subscribe for more! Best wishes! By the way, I think that the wonderful readability of the Feynman Lecture series had more to do with those who surrounded Feynman during its development than with Feynman himself. I've listened to his lectures, not just those in the US but also to many of those done in Australia, and I consider all of them to be rather 'difficult' to access, in the moment. I'm not the only one. Freeman Dyson had to take nearly a year off and drive around with Feynman to grasp his ideas well enough to codify them in terms others could more readily follow and accept. Feynman was clearly a radical at the time. My absolute favorite book about Feynman is "The Beat of a Different Drum" by Jagdish Mehra. I cannot recommend it enough.

[@fabriziosantin7420]

I like your videos and your way of talking/explaining. Keep It up! BTW, this video should be titled "the quantum duck" (or elephant)... "If It looks like a duck, It behaves like a duck, It quacks like a duck, it's NOT a duck, in QM"

[@Mahesh_Shenoy]

Lol! Good one!. Thanks :)

[@marcellis1108]

That was awesome. You’re a great communicator, and I’m really pleased you took the time and effort to create this video. Thank you :)

[@Darisiabgal7573]

The problem with electrons is that they are a faux point particle. This is to say that we can force an electron to be at a point, but only when it undergoes decoherence. If we remember the Heisenberg uncertainty principle deltaX * deltaP ~ planks constant. This describes the fineness of space in which something can be at. This means it cannot simply be a dimensionless point, because in quantum mechanics such points cannot be defined. In fact electrons can undergo field broadening when perturbed in flight as if they are a wave in a field. So if I were to briefly freeze spacetime and place an electron into it and then unfreeze it two things would happen, it would not be in one position and because it has a mass it would begin to resonate. Lambda = h/p. But we need to think about this problem differently, spacetime is not a grid, it has no intrinsic coordinate and it evolves at c. IOW the field is a dynamic equilibrium of the evolution of itself, while it probably does not have true granularity the field at the smallest levels is not precisely uniform with regard to spatial distance or time (if time exists at all at the scales). Something as small as a point of low mass would want to tumble a bit one way or the next until it began to resonate, and this is probably an emergent property of a coherent state. IOW as an electron enters a new coherent state the lowest energy with respect to spacetime is a wobble or a resonance. A good way to think about an atomic electron in resonance is in an orbit in which the orbit is tuned to its wobble. And we can do some crazy mind blowing things with electrons in stable orbitals. There is no reason that an electron has to inhabit an atomic orbital, it can travel freely in space or we can put it between two atoms. We can put it between three atoms, but it really gets happy when it can be spread between 6 atoms, 10 atoms, 14 atoms. So we can lay out a plane of carbon atoms called graphene and up to about 16 microns 2 electrons will try to occupy the whole sheet. At short scales there almost no resistance to the motion of the electron, in fact a psuedo electron is created that is massless. If I drop an electron at one corner, it immediately appears at the other corner without the need for low temperature superconductivity. It’s not perfect, the sheets have imperfections, but the measured resistances are in the E-9 ohm range, lower than any known metal. So why do electrons like to be in these super molecular orbitals. The answer is that these orbitals extend the possibilities of resonation or degrees of freedom of the electron. Even if you don’t drop electrons into the sheet you can detect the molecular resonance at the fringes because the electrons have some affinity to create a traveling wavefront about the grid. If we go back to the double slit experiment the question is what state does a coherent electron want to be in, does it want to be in the initial state or spread out in space like a wave. The answer is not exactly clear, but there is a certain range of uncertainty of motion that electrons can clearly assume and beyond this there is no energetic advantage. So if the electron is perturbed in flight its motion spreads out orthogonal to the direction of travel and even interferes with itself. If we followed it for a long period of time it might reconverge, it’s hard to say or it might time reverse. This tells us one thing about the electron, it does not want to be a point particle, it does not want to be spatially confined. In an atom the nucleus is pulling the electron back to itself, but if the additional options are given, it can spread out between two molecules, 6 molecules and so on. And so we are thinking about an electron wrong, when we fired an electron at a target we are giving it momentum, it is traveling through space and a target is in its path of travel, it eventually is attracted to a positive charge on the target. Thus the target is forcing the state change and the change of state at the target needs to be discrete charge change which can only be satisfied by the contraction of the previous state, the wave function. IOW we are driving the collapse. With sufficient forward momentum the target is essentially giving the electron no choice but to contract the perturbation of its field. It’s not probing the electron for its lowest energy state. And if you think about, atoms are essentially doing the same thing, the positive charge attracts the negative charge, like an asteroid falling into the atmosphere of the planet, the asteroid has little choice but to collide at some point. The electrons can even pass through the nucleus, but they cannot stay there because of the desire to resonate, and so they assume a resonation about the positive charge that is most compatible under the circumstances.

[@simoncliffy]

I'm suspecting this IOW you're speaking of isn't the Isle of Wight?

[@blueckaym]

The reason table-tops are stable when spinning is centrifugal forces. Yes practically everyone knows that, but why specifically? Well the spinning top has some energy, or angular momentum, and we know that it'll spin until it loses its energy. That energy obviously comes from the rotation, but all the particles of the top would prefer to continue on their straight path ... except that they're bound not just by their gravity (like in a star system or a galaxy) but are also bound by the much stronger electromagnetic-forces. But the thing is they're still trying to fly away in straight paths despite being hold back by these forces. And having each particle of a symmetric object pull away at the same time straight-away from the axis of rotation makes that axis stable (though that axis isn't actual physical object - just the line of rotation stability). To be even more pedantic in order to change direction of that axis you have to introduce force in order to affect their momentum, but while Gravity pulls a spinning top directly down - ie on the same line as that axis it's not going to topple the top at least until it loses enough of its energy due to friction and air-resistance. I know that's super pedantic description, and a bit boring to read (for those that understand it), but I hope that it explains the gyroscopic effect to those that didn't know it. :)

[@zebt7477]

There is no such thing as centrifugal force it's a pseudo force. It is only real in a inertial reference frame. So it isn't real .

[@ianoliver3130]

Physics "explains" why a rotating top doesn't topple by "defining" angular momentum (L) to be at 90 degrees to the momentum of the rotating particles within the top. L = R x p. This is purely arbitrary, but helps us to calculate turning forces and precession rates and why it doesn't topple over. It is not an explanation.

[@sr5414-e8i]

I very rarely post, almost never, but I just had to say your explanation was amazing! Although I am a biologist, I have always been fascinated by physics, but when I've tried to understand certain concepts in more depth and found explanations given by physicists (university professors and researchers) for either lay people or high school students, its full of technical terms and equations, none of which actually help a person unfamiliar with the subject to gain a deeper understanding. I started to wonder why physicists were incapable of explaining their subject to a lay person, when chemists and biologists do it all the time. After spending months trying to understand electron spin and giving up, I accidentally came across this video, and now I finally understand what electron spin is!!!!!!!!!!!!!!!! It makes perfect sense. The way you talked through all the contradictions as questions you wanted answers to and gave explanations using terms and analogies that anyone can relate to made it so easy to follow. I only wish there were more physicists like you who could actually give meaningful explanations. Thank you!!!!!

[@sodabutnofizz1294]

I FOUND THE KHAN ACADEMY GUY

[@ethansnow1974]

Yoo I was wondering too lmfao

[@ggor06]

Yeah i recognised the voice

[@RidhaAshir]

YESSS

[@patjakker6730]

Great show but just a question: if it looks like a duck, swims like a duck, and quacks like a duck, then it's probably not a duck?

[@EN_CELL]

what if its some guy with duck costume

[@daves2433]

and if it quarks like a duck?

[@Elaalan_lol]

Think of it like, Gloves and hands - looks the same, sometimes behaves the same BUT not the same. A human and a statue of himself - looks the same, has a name related to the person it depicts BUT not the same.

[@alchemist6098]

You must mean it Quarks like a duck.

[@yashbhat94]

Hi Mahesh, I love how you make all these concepts so accessible. Like I cannot state how simple your explanation is for me to understand (for twin paradox and other non intuitive concepts). I just wanted to mention that for a 3d body, spin is rotation around an axis (not a point) which passes through the body

[@aliam555]

Great video. However, I still see a problem with it. It seems like we have three pieces of information that we are trying to consolidate: 1) electrons have magnetic fields, 2) electrons have angular momentum, and 3) electrons are point-like fundamental particular that cannot spin. I find that parts 1-2 are stronger than part 3 because the former were measured and proven experimentally. Part 3 assumes that a fundamental particle is point-like with zero volume, which was not explicitly measured as truly zero volume. So, when these pieces of information conflict, why we are not concluding that part 3 is incorrect (because parts 1-2 are stronger) and subsequently conclude that fundamental particles do in fact have non-zero volume that can spin instead of inventing a new type of "weird" behavior?

[@RajShekhar-h7w]

Exactly same thoughts. Part 3 seems unfounded and kinda sketchy

[@The-wo4du]

Same thoughts. By the logic that electrons can't spin, we should also say that the centre of a spinning ball is not spinning.

[@len2009m]

That is because on point 3, electrons behave both as a particle and supposedly as a wave. I use the term supposedly because that's what we use to denote the behavior which is not understood in its true sense. That's the explanation for quantum superposition which an electron is always when not observed. Thus we cannot say confidently that its a dot with a non 0 volume and treat it as such cause its not. Its also not a wave either. So its something which doesn't match anything we know of in the macroscopic world.

[@solconcordia4315]

Part 3's problem is with our idea of a "point" , that which has no parts. No matter how many countable number of points we line up together to try to form a line segment with extent, we can *NEVER* form such a line. The term "point-like" is saying that electrons behave differently from being points. They behave as if they have an intrinsic orientation which takes *TWO* 360° complete rotations to return to its original state.

[@KieranLeCam]

You are absolutely right. This is the correct conclusion to come to. And more: if they're not fundamental... what are they made of? Very very exciting stuff! Physics will come around one day!

[@dityaharpatipraja4442]

sir, in brief history of time, Stephen hawking writes that spin is actually the number of times you need to rotate a particle so that it has the same orientation as we started with. for example- if we take an arrow, we need to rotate it 2 times (at 180*) so that we get same orientation as we started with, thus it has a spin 2. Similarly a particle with spin 1 is like a double headed arrow. but electrons behave differently, we need to rotate them 2 times(at 360*) so that it looks the same and it has spin 1/2. how do I reconcile this with u said? your explanation makes more sense to me.

[@Mahesh_Shenoy]

Wait, don't you mean that the double headed arrow is spin 2, a vector gives spin 1 (the most intuitive one), and electrons do spin 1/2. All of that is true. But the key word is spin is 'like' spinning a particle... So, where as in the case of the arrows they are ACTUALLY spinning, in the case of the electrons, they are not. But they do have a property that very much resembles the classical spin -aka - the magnetic dipole moment and Larmour precession. It's not actually turning the particle in the classical sense. That's the whole message of the video.

[@DrDeuteron]

Wait, an arrow is spin one. A bar magnet has this symmetry. It needs 360. Linear polarized light intensity has spin 2 symmetry, so you wear polarized sunglasses upside down , 180, and they still work. Spin is 1/2 and is the fundamental spin able object, but it hard to visualize. Now I say spinable, bc spin 0, like a helium atom in the ground state, is perfectly spherical, and it cannot be rotated. A rotation is equal to doing nothing (multiplying by one, really).

[@jorgepeterbarton]

Another video explaining what not spinning but acting as if HALF spin really means. I imagine difference outcome of angular momentum and charge, like values that would be impossible for a classical object like a top or magnet, just different values but what does it really mean

[@ianoliver3130]

​@@Mahesh_ShenoyThanks. The electron is not spinning but it's property of magnetic dipole exists "as if" it were spinning. Important to remember that physics isn't meant to "explain" nature, but to describe it- by comparing it to other phenomenon which behave in a similar fashion. Hence the angular momentum of the electron.

[@coniccinoc]

Wow, I swear to you, not joking, trying to understand electron spin kept me up last night. This video game me the understanding I wanted. You are a highly gifted teacher!

[@GodSahil]

I really liked your last lines that "we have no intuition for that quantum world" But it would be really great if we could go to the quantum world and maybe see the world with our own eyes 👀

[@AurelienCarnoy]

I totally disagree. I think we can get intuition, Stick a belt in a book. Twist the belt once. Try to untwist it by passing the brlt under the book. It spins without spinning. Space time is spinning.😅 On an other note, It would be fun to imagine that all the electrons are actually one. Then it is just space time between each electron that is different.

[@GodSahil]

@@AurelienCarnoy haha, very cool! But still, we can't explain every concept of quantum theory with our daily experiences.

[@l.h.308]

But alas, would we not collapse everything there by looking with our eyes?

[@themulticourse2460]

​@l.h.308 what is seeing? And how do we see? When photons strike object and Enter our eyes we see. But in quantum world photons will be bigger than us so we won't be able to see eternal darkness

[@you_are_kidding_me_right]

If an electron isn't spinning but has angular momentum and therefor is acting like it's spinning, could it in fact be vibrating?

[@aidenharris5751]

You along with a couple other channels have made me decide that after aerospace, i’m doing particle physics

[@theotheroneb1548]

What the hell is 1/2 spin though ?!?

[@Rajbanerjee518]

Yes i have a doubt in this case,with our syllabus of jee adv,what acutal meaning of +1/2 and-1/2???????????🙄🙄😑

[@ankitmaharshi6623]

Half spin mean there are only 2s+1 orientation of spin possible in presence of meganetic field. If one electron placed in megnetic field it can have only two orientation either oppose or in the similar direction of the megnatic field. So according to the formula spin of elctron must be half. If an electron have 1 spin than its three orientation possible, and you can catch it in the resonance spectroscopy like esr

[@FlorianProck-Schauer-j2k]

there is a great explaination if you view the set of possible Rotations as a set of continuous paths on a Disc(where opposite points are being identified as the same points). In this picture Rotations by 4pi can be continuously transformed into a Point(no rotation at all) while Rotations by 2pi cannot. Therefore this can be seen as an analogy to Objects with Spin 1/2 which have e^(i*1/2*4pi) = 1. I know this does not explain everything but it shows that spin 1/2 actually can make sence in that way.

[@manabouttown7865]

Why don't we assume that electron has an internal structure?

[@shashwat._.03]

Because, as he said, electrons are fundamental particles themselves. Why don't we assume quarks have an internal structure? Exactly.

[@TheMaolol]

​@@shashwat._.03how do you know they are fundamental particles?

[@sumayya10a55]

There are theories like string theory which says this. But ppl are not believing it. It actually calls string as the fundamental particle which vibrates in 11 diff dimensions

[@synapticmemoryseepage4447]

Very interesting and fun. I like Mahesh's argumentative approach with Feynman.

[@Achrononmaster]

@15:00 it is probably not as mysterious as you make it out to be. You need to understand spin=1/2 is a symmetry group representation, not a model of a charged current. So "quantum spin" only means the fermions have a spinor representation (they transform as rotors under Lorentz and space rotations). It is a slightly separate matter whether the fermion has a circulating mass current. They seem to since we measure a magnetic moment. The idea this is something "internal" is nonsense, because at least for the charged fermion we measure the magnetic moment which is a spacetime measurement, not some internal fibre bundle space. There could be some subtle local nontrivial spacetime topology, but even then, that's not so mysterious. It's just not detail we can probe.

[@woops9076]

“That’s not so mysterious. It’s just not detail we can probe.” Is that not what mysterious means?

[@GodSahil]

3:10 But what if we found out the electron is still made up of smaller particles in the future. 😂

[@Mahesh_Shenoy]

Great question, I actually edited this out to reduce the length :D. Anyways, that's the besides the point! We BELIEVE that electrons are fundamental particles. So everything else we believe should be consistent with this belief. That's why we can't also BELIEVE that electrons are spinning like a table top. Fun fact: We did try to figure out how big the electron needs to be for it to spin like a top and produce the magnetic field it does. The size came out to be larger than the atom itself!

[@GodSahil]

​@@Mahesh_Shenoynice fact ✌

[@harleyquinn8202]

@@Mahesh_Shenoy Electron is perturbation of a quantum electromagnetic field - a king of wave that spreads beyond the atom it is in. Why that perturbation cannot behave like a tiny cyclone in that quantum field?

[@TankEsq]

​@@harleyquinn820210:55 angular momentum experiments would probably have different results if that was the case

[@ianoliver3130]

If the electron turns out to have smaller particles within it, then we will simply change our model of explanation. Physics has done this multiple times.

[@GSPV33]

You have a very pleasant voice as a speaker. More relevantly, i appreciate your enthusiasm and pace. This was very interesting.

[@agytjax]

But WHY shouldn't fundamental particles NOT SPIN about their axis ? This seems to be a big assumption made by Feynman, but I would love to know why ?

[@amenoum7623]

In short, it would have to spin faster than light, and that is not allowed by Special Relativity. But there are other theories. I have one, and it predicts electrons have real mass and charge radii (albeit different) and are actually spinning faster than light. By the theory, speed of information is not absolutely invariant to scale, rather inversely proportional to scale. The non-intuitive and absurd phenomena of QM are just a non-intuitive and absurd interpretation of reality. These are not facts, even though they are commonly presented as such.

[@sylvan429]

the explanation in the video is that spin is an emergent phenomenon, and therefore a single electron can't spin (because it can't exhibit emergent phenomena)

[@sylvan429]

I think in even more simplified language, according to my understanding, in order for spin to occur there needs to be different parts of the object with different velocities... but you can't apply different forces to different parts of an electron, because it's not composed of anything smaller.

[@shreyash3903]

Mahesh craking social cues and debunking pseudoscience with science

[@Mahesh_Shenoy]

Haha!! Always!

[@InexcyeSolms-handle-is-taken]

Well done, sir. Not just for the knowledge you deliver, but the spirit you deliver with.

[@VJMusic01]

Can anyone tell about which pseudo scientist he is talking about at #4:49

[@LearnerXavier]

Plz tell anyone

[@VJMusic01]

I'm still waiting!

[@jordandilley9731]

Glad I’m not alone

[@arthurmassenataube8085]

I love you videos, you can explain hard topics so clearly. English isn’t my main language, but you talk simple and slow, so I can understand. Thank you very much.

[@conflict_monitor]

Quite possibly my fave physics exposition channel. Kudos

[@tablettorrensabellan]

Several hours viewing eigenchris and Noah explains physics series on spinors and spin...with great profit....and also viewing tens of videos on spin.... And Mahesh has given me some important clues that missed... In just 15 minutes!! Bravo Mahesh!! , and thank you!!!

[@doctorvimalkatarmal4704]

Bro..literally this is the best you tube channle I found..because in starting of every video u start with the problem we face to understand the basics..you first solve our doubts then come to topics... like in this video you cleared that group of partials could spin not a solo one..yeh boom.. common sense still 8 years of watching videos I didn't found this point... Thanks you bro...I love physics and you made it easy for us..😊

[@Anders01]

I recently learned about an old concept called the Parson magneton which I found fascinating. If I understand it correctly then the electron is like a spinning torus around the nucleus and I imagine that something similar to +/- 1/2 spin can be achieved through the nucleus doing a "pole shift". And also if the torus is made of standing waves that could perhaps represent the quantized energy levels of an electron.

[@Endrit719]

This channel has become my go to for bedtime stories, I love how you explain also I love that you can talk and ask questions to all scientists like Einstein and now Feynman, very lucky guy

[@Jon.B.geez.]

I don’t agree with some of the assumptions made especially about what constitutes spin. However, VERY insightful video! I plan to watch again in some months. Some notes I must take for now

[@Almamunkhan]

just had a perfectly describing about something which I couldn't really understood entirely with a thousand of trying. maybe it is still incomplete or understood but had a great idea and enjoyed how you reassembled everything together,

[@logan711]

i always feel like i ask slightly dumb questions a lot. i feel like theyre not really dumb, but it only seems that way because it goes against the text book, but for every wonder crossed off, your boundaries get closer and closer to grasping the topic. this video did a pretty good job doing that

[@rhsmn2334]

lmao 11:53 the black rectangle on the (very mildly, so mildly in fact that i wouldn't have even thought it was had you not highlighted it) balding spot you're a cool guy with a great sense of humour and an amazing science communicator

[@antilog5851]

I recently found your channel and i am ...... so sooo glad that i did. Your content is amazing. I also have the same doubts and you exactly address those. Thank you. You got a new subscriber, and that too , a regular one.😊

[@NamiZu00]

The first time I actually understood why it is called spin, thx for the informative content!

[@ravipande8639]

Thanks Mahesh! You made an incredibley difficult to imagine topic (human beings need to imagine and visualise the topic to understand it) so simple that for the dirst time I could visualise and imagine what electrin spin is. Keep it up.

[@samiulhaquerounok5787]

Only one channel which gives the actual feelings of science.

[@RWBHere]

I love your emergent properties example of the cell. Thanks. Great explanation of what is meant by 'spin'. 👍

[@dipendrabhatt8789]

I am a software engineer and was deeply interested in computers and physics. But chose computer for the career path, and i am here watching your videos at 12 in the night. It has become kinda like my winding down ritual. And i have got to say, each of these videos answer a question which back in the day, we always would answer by what you already termed "psuedo science" but never understanding the true intricacies. While i am not saying i became an overnight expert on these, but the intuitive way on how you make videos is so fun to watch. Hell i even watched half of this video back in the gym when I was doing boring cardio on the treamill.

[@sharminmim8430]

Best ever spin explanation to me ..... Thank you so much ❤

[@nicolaskrinis7614]

Nicely explained. In the end, spin is really quantisized angular momentum . Another reason why it doesn't intuitively spin is because it would need to spin faster than the speed of light.